Voltage divider



Oct. 7, 1952 E. H. osTERLAND VOLTAGE DIVIDER Filed June 5, 1946 Patented Oct. '7, 19.52

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osieriand, Farsiiipaiy, NiiJ.; Application Jones; incastrarmicincue- This invention relates toy alternating-current voltage,- dividers and: `in particularto those, ofi the'l capacitortype. Such dividers aref-oftenreferred to as-meter multi-pliers.

The general object ot the inventionv is to prio-iu vide :in-improvedvoltage..l divider ofthe capacitor' type that will produce a step-down from af high voltage, high frequency source inv suiii'cient1 dexgree to permit the input` voltage'to be. mustaccurately` measured by means ofiv an ordinary. vacuum tube vol-tmeter or other highy input impedance voltmete.

A specific object isto provide a capacitor type voltage divider in which theeffectofstray capaci-- itances is reduced to a negligible factor,l thereby resulting in! a higherdegree. ofmeasuringt ac.. curacy and permitting use-of a; much -sma-llercaf-f` pacitor unit in the' divider than heretofore possible, thus keeping the circuit loadingto a mini` mum'.

Another object. is to provi-'de acapacitor'type. voltage divider which oiers a. stepupvofl impede ance with respect to theA output terminals so that' the measuring device imposes a smaller-' load-upon' the source beingv measured..

Yet another object is to providea meter multiplier for use in. measuring high voltages. featuring' short input' connections but which atV the. same time permits the voltmeter instrumentitself to be located at a, safe distance from thevol'tage source being njieasurecl.`v

The foregoing a-ndother objects and advan tages of the invention will become more apparent from the following detailed description and fromV theaccompanying drawings in Which:

Fig. 1 is a view inverticalsection ofyapreferred` construction accordinglto theinvention;

Fig. k2 is a transverse section taken yon* lines 2.-2'ofFig-.1; v,

Fig.v 3 is an electrical schematic showing the circuit of. the capacitor arrangement.i1i-F{ig.. lf;v

Fig; 4 is. a vertical viewy ofl a modi-fied constri-ier tion, partly in. section and partlyv i-n'elevation; and

Fig.l 5y is also an electric-al the circuit arrangement of the resistor and ca-` pacitor components in the.; Fig. li-embodiments Referringl now to the, drawings and in particu-- lar. to Fig'. 1, the improved construction accor-.d-vv ing to this invention features a tubular envelope- I0 of dielectric material, preferably of; glass.. As shown in the drawing, envelope I.-0 should be evacuated such as' byy conventional vacuum pump apparatus through tip I0a. vvheri thev voltage dij-iy vider is intended for use Wherey conditions reschematic shovvingi .J

s claims. (craze-191i:

y quita comparatitely iovt.input.L capacity. and'. a. h iglhi breakf-downfprotectiort in` smallV space...`

However; inisoine-.caseshenvelopa Iifmay be filled.

withia. substanceisuchfas transformer oilfi'nporden toiinorease thefdielectric' constant" andi hence the;

input capacitive Y The upperportion-tuo oii the envelope. it. is corrugated; to. increase the leakage pa'tli...while the' lcv/er* pention.. lilo isP shaped-.fasi a. cylinder. Projecting into the;- envelope` through. the` upper..

end is ani electricallyy conductive-- rod" ILII.l Thisy rod may.. bef4 constructed. ofitungsten or Koi/ar or-othen metal; whichi seals Well to the particular. grade ofV glass use di and; whichc rod. is., fairly rigid andi. strong Thelatter: is positioned'. along: the

longitudinalaxisot'thefenvelope.anditslowerend. is' enlarged to form a cylindrical electrode. mem..

ben t2, which isv disposed. within. the. cylindrical portion I'Uc off theenvelope.Y Thet upper end` of. roda lIwservesi. asi-the high`r voltage connecting pointe. The outer'. surface.ofA electrode I2 forms oneplateof? acapacitoc C1...v The other plate off capacitor Crl is forinedj-byx a; layer of electrically` conductive-z material.` If3 whiohlcovers the cylindricaliand bottoni; portions of envelope l0. The` conductive layer I-3- is, preferably the form. of a coating Whichi can loe-,Yv applied by?dipping,V sprayingI on brushing and,A preferably, the coating is;l baked toinsure stability. Pyro-chemically depositodv silver" or colloidal carbon. solutions. may be used with equivalent results for this purpose.. A- conductive lead I4 secured by and'. projecting through thebotto-m wall off envelope I0r contacts coatingy i3 provide an electricalA connection A1 layer; et. insulation suchas sleeve. I5. maden `from-a: material having a,l high qualitylinf. sulation. characteristic as-,. forxexampia Bakelite or polystyrene tubing overiiesfand ts on conductive coatingy [3v-,1 and. ametaliio laver'sicti asa sleeve I:6 which may be of brass overlies. andi Similarly tted yon the insulating sieeve I5; When-separate insulating or` conducting'sleeves` are used'f',v the assembly can bie secured piaeeby means oia suitable cement such as Buca It is also possible, ofA course, to form either or' both fineseiayers by the use off liquid deposits which harden to form the desired coat. SIeii Itgthe With the QXble metallic Shield [11i fcabl'e1l7. constitutes one plate of anotherv capacitor, Ci.. The other plat-e off the latter c apacitorjisl constituted' by the outersurface of conductive, coating I3 While. the insulating, sleeve I5 'I and the insulation I'Ic of cable Il' serve as the chanically connected by soldering to the collar.

ISa attached to metallic sleeve I6. Assuming one side of the voltage source to be measured to be electrically grounded, sleeve II. would vlike;

wise be grounded through shield IIb as indicated on the drawing. Connection to the vacuum tube down ratio of 100 to 1, C2 would have a value of 200 md, etc. These values of C2 do not take into account the capacitive loading due to the particular voltmeter used. In practice, of course, the voltmeter input; capacity is subtracted from the ideal values indicated here to produce the actual magnitude of C2.

If the construction is as shown in Fig. 4 in which resistors R1 and R2 are used, the ratio of R1 and R2 should be the same as the capacity between C1 and C2. e

In conclusion, it will of course be understood that while preferred embodiments of the invention have been illustrated in the drawings, various changes in the arrangement of parts may be made without departing from the spirit and scope of the invention as defined in the appended claims.

or other high input impedance voltmeter is made 1 to the shield I'Ib and conductor I'Ia. as indicated.

'I'he conductive coating I3, insulator sleeve I5 and outer metallic sleeve I6 extend to the junction between the corrugated and cylindrical portions of envelope I0. 'I'he outer metallic sleeve I6 provides electrostatic shielding of the essential operating portion of the voltage divider and thereby reduces the possibility 'of "stray capacity pickup to the conductive coating I3.l

Referring now to the schematic 'diagram in Fig. 3, it will be seen that capacitors C1 and C2, are arranged in series, and that the voltmeter connections are tapped across the plates of capacitor Cz. If desirable, the capacitance of capacitor Cz may be altered for fine adjustment of the percentage of step-down in voltage by connecting externally mounted capacitors of standard design in parallel therewith inthe usual manner.

If the input voltage to be measured contains low and medium audio frequency components in addition to the higher frequencies, resistors should be connected in parallel with the capacitors C i, C2. Such an arrangement is shownv in the modified construction illustrated in Fig. 4. Except for the resistors, the Fig. i structure is like that of Fig. l and hence like reference numerals have been used to designate corresponding parts in the two views. In the modied construct-ion, a resistor R1 is connected between electrode I2 and lead I4, and'a secondresisto'r R2A is connected betweenlead I4 and the grounded metallic sleeve IB.

As shown in Fig. 5, the modified voltagel divider according to Fig. 4 comprises capacitors C1 and C2 connected in series across'the high voltage input terminals, and resistors R1 and R2 connected in parallel with capacitors C1 and C2, respectively. Like the Fig.'1` arrangement the voltmeter is adapted to be connected across the plates of capacitor C2.

In both the Fig. 1 and Fig. 4 constructions, the physical dimensions: of the voltagel divider and the electrical values of the capacitors vand resistors used will be dependent upon the voltage with which the device is intended tobe usedmand the desired voltage step-down ratio. In the illustrated embodiments of the voltage divider, the drawings are to scale and are somewhat smaller than full size for use on a ten thousand volt source. The capacitance of capacitor C1`l for such a divider would be from 1-3 auf, and the capacitance of capacitor C2 would vary dependent upon the desired range. Thus for a step-down ratio of 10 to 1, and assuming C1 to have a capacitance of 2 auf, Cz would be 20 auf; forl a step- I claim:

"1. A voltage divider of the capacity type cornprising an envelope of dielectric material, an electrode supported within said envelope, voltage input terminal means connected to said electrode, a rst conductive layer on the exterior' surface of said envelope forming with said electrode the plates of airst capacitor, a layer ci dielectric material overlying said iirst conductive layer, and as econdconductive layer overlying said dielectric layer and substantially the entire Vsurface area of said first conductive ylayer to constitute a shield for the layer against stray electrostatic fields, said rst and second conductive layers forming the plates of a second capacitor constituting a measuring output adapted for connection to a high .impedance voltmeter. l

2. A voltage divider of the capacity type comprising an envelopel of dielectric material, an electrode supported within said envelope, a voltage input terminal extendngfrom said electrode through said envelope, a conductive coating on the exterior surface of said envelope forming with saidl electrode` the plates of a first capacitor, a sleeve of dielectric material overlying'said conductive coating vand a vmetallic sleeve overlying both said dielectric sleeve and substantially the entire surface area of said conductive coating to constitute a shield for the latter against stray electrostatic fields, said coating and metallic sleeve forming the platesvof a second capacitor andconstituting a measuring'output adapted for connection to a high impedance voltmeter.

3. A voltage divider of the capacity type coinprising an envelope of dielectric material, said envelope having anupper corrugated portion and a lower cylindrical portion, a cylindrical electrode supported centrally within saidenvelope at the cylindrical portionl thereof', a voltage input terminal extending from lsaid electrode through said envelope, a conductive'coating on the exterior cylindrical surface portion of said envelope forming with said electrode the plates of a iirst capacitor, a sleeveof dielectric material overlying said conductive coating, and a'metallic sleeve overlying both'said dielectric sleeve and substantially the entire surface area of said conductive coating to constitute a shield for the latter against stray electrostatic elds, said coating and metallic sleeve forming the plates of a second capacitor and constituting a measuring output adapted for connection to a high impeclancevoltmeter. 1 y

' 4. A voltage divider of the capacity type comprising an envelope of dielectric material .said envelope having upper corrugated and lower cylindrical surface portions, a voltage input terminal rod extending into said envelope at its upper, y

end, a cylindrical electrode at the lower end of said rod and disposed at the cylindrical portion of said envelope, a conductive coating on the exfterior cylindrical surface portion of said envelopeforming with said electrode the plates of a r's't capacitor, a sleeve of dielectric material overly- "ing said conductive coating, and a metallic sleeve overlying both said dielectric sleeve and substantially the entire surface area of said conductive coating to constitute a shield for the latter against stray electrostatic fields, said coating and* I metallic sleeve forming the plates of a second capacitor and constituting a measuring output adapted for connection to a high impedance voltmeter.

5. A voltage divider of the capacity type comprising an envelope of dielectric material, said envelope having upper corrugated and lower cylindrical surface portions, a voltage input terminal rod extending centrally into said envelope through the upper end thereof, a cylindrical electrode at the lower end of said rod and disposed A `within the cylindrical portion of said envelope,

a conductive coating on the exterior surface por` tion of said envelope forming with said electrode Athe plates of a first capaciton'a sleeve of dielectric material overlying said conductive coating,` a metallic sleeve overlying both said dielectric sleeve and substantially the entire surface area of said conductive coating to constitute a shield capacitor, the other plate of which is constituted by said metallic sleeve and shield member of said cable.

EDMUND H. OSTERLAND.

REFERENCE S CITED The following referencesy are of record in the file of this patent:

UNITED ST-ATES PATENTS Number Name Date 1,590,420 Chubb June 29, 1926 1,610,980 Silberman Dec. 14. 1926 1,796,254 Nyman Mar. 10, 1931 1,934,475 Bailey Nov. 7, 1933 1,995,839 Buschbeck Mar. 26, 1935 2,046,450 Fausett July 7, 1936 2,135,338 Higgins Nov. 1, 1938 2,161,888 Rearick June 13, 1939 2,330,822 Fischer Oct. 5, 1943 

